When studying economics you will most likely begin learning about it by studying a subsection of the overall subject. The subsection that you will generally start learning about is microeconomics. Once you have studied microeconomics you will normally move onto macroeconomics.
Essentially, microeconomics look set issues and theoretical ideas related to economics on a smaller level. For example, you may look at how individual businesses with in an industry can become more efficient. Alternatively, microeconomics looks at things on a far bigger scale, and may look at how governments impact upon the economy or how industries operate. Once you have a decent understanding of the two sides of economics, you can sometimes use them in conjunction with each other. For example, you may look at how an individual business would operate in a certain market structure.
Once you have an understanding of the difference between microeconomics and macroeconomics, it will make it far easier to pick a good topic to write term paper about. Of course, if you have been studying microeconomics and there is something that you have particularly enjoyed or found interesting then you may wish to write about that. Alternatively, if there is a particular aspect of microeconomics that you feel you are best at then you may wish to try and maximise your chances of doing well on the essay by writing about that particular concept.